Microphone having a protective cap

ABSTRACT

A microphone includes a microphone housing having a sound transducer therein. A cover of substantially cup-shaped configuration fits over one end of the housing above the transducer and it is made of a material which comprises a plurality of particles which are sintered together or fused together in a manner to define tortuous passages therebetween and to define hollow spaces remaining between the particles, and which hollow spaces are interconnected, thus forming irregular channels which assure the sound permeability of the cap but are impenetrable by dust or other air pollutants.

United States Patent Weingartner [4 1 Mar. 28, 1972 MICROPHONE HAVING Ai 1 References Cited PROTECTIVE CAP UNITED STATES PATENTS 1 lnvemorl WWelngmner, Mauerbers, 2,702,318 2/1955 Dvorsky ..179/121 1) ma 3,236,3282/1966 Burroughs ..l79/l84 [73] Assignee: Akustische U. Kino-GerateGesellschaft 2,556,168 6/1951 Cragg a1 -179/184 Vienna, Austria2,444,620 7/ 1948 Williams et al. ..l79/l 10 [22] Filed: May 1970Primary Examiner-Kathleen l-l. Claffy [211 App} NOJ 31,863 AssistantExaminer-Thomas W. Brown Attorney-McGlew and Toren Related US.Application Data [63] Continuation of Ser. No. 542,419, Apr. 13, 1966,[57] ABSTRACT abandoned. A microphone includes a microphone housinghaving a sound transducer therein. A cover of substantially cup'shapedcon- Foreign Application Priority Data figuration fits over one end ofthe housing above the trans ducer and it is made of a material whichcomprises a plurality Apr. 23, i965 Austrla A374 2 of particles whichare Simered together fused together in a [52] us Cl I I I "179/184179/179 manner to define tortuous passages therebetween and to 511m.c1.IIILI.....IIIIIII.I.IIII.....IIIIIIIIIII ..l-l04rl/08 defineSpaces remaimng between Particles and [58] Field of Search ..179/121 D184 which Spaces are imemnnected, fmming lar channels which assure thesound permeability of the cap but are impenetrable by dust or other airpollutants.

9 Claims, 1 Drawing Figure I g 8 I 817" A 6 50 JAN/\JAL PATENTED MAR 28I972 INVENTOR BERN HARD WEIN6/IRTNER MM W ATTORNEY 5 MICROPHONE HAVING APROTECTIVE CAP This is a continuation of application Ser. No. 542,419,filed Apr. 13, 1966, now abandoned.

This invention relates in general to microphone construction and inparticular to a new and useful microphone housing and cover constructionand to an improved microphone cover composed of three-dimensionalparticles which are sintered together.

Microphones are usually provided with a protective cover which protectsthe thin and extremely delicate diaphragms of the transducer system frommechanical damage and prevents penetration of dust and dirt particlesinto the transducer system. Such covers are usually made up of aplurality of separate part elements which are fitted together; forexample, they usually include a rigid part or mechanical protection anda filter element consisting of a very fine meshed wire or gauze fabricfor the protection of the transducer system from dirt and similarimpurities. The mechanical protection part may require a considerablemanufacturing expense and may comprise, for example, a thick stiff wireformed into a hemispherical structure or a hollow body of plastic ormetal material which is formed with sound inlet apertures. Sometimes afurther layer is added which comprises a sound permeable material suchas a foamed plastic or nonwoven textile or the like which also affordsprotection against Wind. In spite of the expense of manufacture, thesecovers have the disadvantage that iron particles may penetrate into themicrophones and interfere with the function thereof especially if theybecome deposited in the narrow gap of the microphone, particularly inelectrodynamic microphone, particularly in electrodynamic microphoneswhich have a working air gap permeated by a very strong magnetic field.

In accordance with the present invention the disadvantages of the priorart are overcome by providing a cover which is formed of a sinteredmaterial having particles of spherical or irregular shape which areformed together into a single cover element, which is capable ofperforming all of the functions required for protection and operation ofthe microphone. In the preferred arrangement of the invention, thesintered material of the cover comprises preferably metallic particlessuch as spherical bronze particles about 0.7 to l millimeter indiameter. In special cases where a lesser filtering action will besatisfactory, it is possible to use a sintered plastic materialcomprising spherical particles of thermoplastic material which arepartially sintered together. In accordance with a feature of theinvention, the wall thickness of the protective cover should not exceedtwice the diameter ofa spherical particle of the sintered material. Acover made up of sintered particles constructed in accordance with theinvention provides an extremely high mechanical stability as well as apleasing appearance in spite of its great strength. When the particlesare sintered together into a cover construction, they have a sufficientspacing for sound permeability, but they define a tortuous and long pathfor the flow of impurities with the inflow passage being regularlycurved and provided with corner spaces where the impurities will depositbefore they can enter into the microphones. A further advantage is thatsince the sound waves must also traverse a relatively long path into thetransducer portions of the microphone there is an inherently goodprotection of the microphone from the effects of wind.

Accordingly, it is an object of the invention to provide a microphonehousing and cover construction in which the cover is easily and simplyfitted over the housing and is made of three dimensional particles whichare sintered together.

A further object of the invention is to provide a microphone cover whichis made up of sintered particles such as spherical bronze particles offrom 0.7 to 1 millimeter in diameter, plastic particles and the like,which provides a safe protection of the microphone from dust andimpurities and which provides for satisfactory sound transmissions.

A further object of the invention is to provide a microphone cover and amicrophone cover and housing construction which are simple in design,economical to manufacture and rugged in construction.

The various features of novelty which characterize the invention arepointed out with particularlity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawing and descriptivematter in which there is illustrated and described a preferredembodiment of the invention.

The only figure of the drawing indicates a partial elevational andpartial transverse sectional view of a microphone constructed inaccordance with the invention.

Referring to the drawing, in particular, the invention embodied thereinincludes a microphone housing generally designated 1 which is of tubularconfiguration and includes an upper flared portion 3. The upper flaredportion 3 includes an internal annular recessed portion 3a defining aledge 7 which forms an annular seat for a transducer assembly generallydesignated 2. The transducer assembly 2 includes a collar portion 8having a top bevel 8a and a bottom bevel 8b. The bottom bevel portion 8bfits into the recess 3a and conforms to the side walls of the recess 30and the microphone transducer assembly 2 rests on the ledge portion 7.

In accordance with a feature of the invention, the housing is formed ina simple manner so that the transducer assembly 2 may be positioned onthe groove 7 and secured in position such as with securing bolts 6 whichextend through the wall of the flared portion 3 into the collar 8.

In accordance with a further feature of the invention, the microphoneincludes a unitary construction cover or cap 5 which is made up of aplurality of particles, preferably metallic particles such as sphericalbronze particles of from 0.7 to 1 millimeter in diameter, which aresintered or fused together. In the embodiment illustrated, the cover 5is made of a cupshaped configuration and it has a top wall 5t which issound permeable and internal walls 5a and 5b which are of the same slopeas the bevelled portion 8a of the collar 8 so that the cover may beeasily positioned thereover. In some instances, it is also preferable toprovide securing screws (not shown) similar to the screws 6 which willextend downwardly through the cover 5 into the collar 8. Where only asmall filtering action is desired, it will be possible to form the cover5 of a sintered plastic material such as spherical particles ofthermoplastic material. In the preferred arrangement, the wall thicknessof the protective cover could not exceed twice the diameter of aspherical particle of the sintered material which is used to make thecover. The term sintering is used in this specification to indicate acaking together of material particles at elevated temperatures and isgenerally used to be synonymous with the term fused which is alsoemployed herein. When the particles are sintered, they bond together atthe points of contact and where they are not in contact a cavity remainswhich communicates with the next adjacent cavities so that a channel orpassage is defined through the sintered material and such passagesbecome finer or smaller the smaller the dimensions of the sinteredparticles are.

The protective cover 5 may be matched to various housing materials bysuitable surface finishing treatments such as anodizing, electroplating,etc. When it is made of sintered plastic materials, the materialsemployed may be of different colors.

The sintered material which constitutes at least the top 5: of theprotective cover 5 and advantageously also the side walls 5a and 5b mustbe permeable to sound so that the sound will be transmitted through thecover without any modification. This is achieved through themultiplicity of passages which are formed between the sinteredparticles. Because of the sintered structure of the cover 5, thesepassages are nonlinear so that they will not permit a laminar flow ofair through the cover.

The particles which are sintered together may be spherical or may havean irregular shape.

The protective cover 5 has various advantages over covers of othertypes. It has an extremely high mechanical stability and a pleasingappearance in spite of its high strength. The

path to be traversed by any impurities which would tend to enter throughthe protective cover 5 will be much longer than a corresponding path,for example, in a well known protecting device such as a gauze shield,for example. The path defined between adjacent particles which aresintered together is irregularly curved and is provided with cornerspaces or dead areas which trap any impurities and insure that theycannot inflict damage. The fact that sound must traverse the protectivecover along a relatively long path provides a good protection againstwind interference.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the inventiveprinciples, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

1. A dynamic microphone construction comprising a microphone housing, adynamic sound transducer mounted in said housing, and substantiallyacoustically neutral shielding means for protecting the transducer andfor minimizing the effect on the acoustic response of said transducer tosound outside the shielding means, said shielding means forming a coverfor said housing extending over said sound transducer, said cover beingof unitary construction and made up of a plurality of three dimensionalparticles sintered together and defining tortuous passages therebetweenand defining at least one sound permeable wall portion adjacent saidtransducer; said cover, with said sound transducer, defining a largevolume air space, and being spaced from said transducer; said coverbeing self supporting, the sintered particles defining tortuous soundwave air passages to trap impurities and to protect against windeffects.

2. A microphone according to claim 1, in which said three dimensionalparticles are substantially spherical.

3. A microphone according to claim 1, in which said three dimensionalparticles have an irregular shape.

4. A microphone according to claim 1, wherein said particles are metal.

5. A microphone according to claim 1, wherein said three dimensionalparticles are spherical bronze.

6. A microphone according to claim 1, wherein said three dimensionalparticles are spherical and are synthetic plastic material.

7. A microphone according to claim 1, wherein said particles have adiameter in the range from 0.7 to 1.0 millimeters.

8. A microphone according to claim 1, wherein said cover has a wallthickness which is approximately twice the diameter of said threedimensional particles.

9. A microphone according to claim 1, wherein said housing issubstantially tubular and includes an upwardly and outwardly flaring tipportion, said upwardly flaring portion having an internal annular recessdefining an annular ledge at the bottom of said recess, a transducerassembly supported on said ledge, said transducer assembly including acollar having a bevelled edge complementary to the surface of saidrecess and further including an upwardly and an inwardly bevelled topedge, said cover including a flat top portion and two divergent sidewall portions, said side wall portions having a slope complementary tothe bevelled top edge of said annular ring of said transducer andfitting therearound.

1. A dynamic microphone construction comprising a microphone housing, adynamic sound transducer mounted in said housing, and substantiallyacoustically neutral shielding means for protecting the transducer andfor minimizing the effect on the acoustic response of said transducer tosound outside the shielding means, said shielding means forming a coverfor said housing extending over said sound transducer, said cover beingof unitary construction and made up of a plurality of three dimensionalparticles sintered together and defining tortuous passages therebetweenand defining at least one sound permeable wall portion adjacent saidtransducer; said cover, with said sound transducer, defining a largevolume air space, and being spaced from said transducer; said coverbeing self supporting, the sintered particles defining tortuous soundwave air passages to trap impurities and to protect against windeffects.
 2. A microphone according to claim 1, in which said threedimensional particles are substantially spherical.
 3. A microphoneaccording to claim 1, in which said three dimensional particles have anirregular shape.
 4. A microphone according to claim 1, wherein saidparticles are metal.
 5. A microphone according to claim 1, wherein saidthree dimensional paRticles are spherical bronze.
 6. A microphoneaccording to claim 1, wherein said three dimensional particles arespherical and are synthetic plastic material.
 7. A microphone accordingto claim 1, wherein said particles have a diameter in the range from 0.7to 1.0 millimeters.
 8. A microphone according to claim 1, wherein saidcover has a wall thickness which is approximately twice the diameter ofsaid three dimensional particles.
 9. A microphone according to claim 1,wherein said housing is substantially tubular and includes an upwardlyand outwardly flaring tip portion, said upwardly flaring portion havingan internal annular recess defining an annular ledge at the bottom ofsaid recess, a transducer assembly supported on said ledge, saidtransducer assembly including a collar having a bevelled edgecomplementary to the surface of said recess and further including anupwardly and an inwardly bevelled top edge, said cover including a flattop portion and two divergent side wall portions, said side wallportions having a slope complementary to the bevelled top edge of saidannular ring of said transducer and fitting therearound.